Detection Of Knockdown Resistance (Kdr) In Cimex Lectularius And Cimex Hemipterus (Hemiptera: Cimicidae)

Abstract:
Worldwide, there are many reports of pyrethroid resistance in bed bugs (Cimex spp.). Previous studies on the Common bed bug, Cimex lectularius L., have identified two mutations (V419L and L925I) in the voltage-gated sodium channel (VGSC) gene responsible for knockdown resistance (kdr). However, nothing is known on possible kdr mutations in Australian strains of C. lectularius or on the Tropical bed bug, C. hemipterus F. This study aimed to identify the status of kdr mutations in Australian C. lectularius strains, and C. hemipterus in Australia and international strains. Samples of C. lectularius were obtained from 24 sites across Australia, while the C. hemipterus were sourced from Australia, as well as Africa, India, Malaysia and Thailand. DNA was extracted, purified and examined for the kdr-related genes by PCR and Sanger sequencing. In C. lectularius field populations, the haplotypes A (neither V419L nor L925I), B (L925I only), and C (V419L and L925I) were found, with most (88%) of the field populations being haplotype B. A novel mutation, I936F, was identified in an ‘Adelaide’ strain (initially identified as haplotype A), which may be linked with kdr-type resistance. In C. hemipterus, the V419L and L925I mutations were not detected, however, three novel mutations, M918I (Methionine to Isoleucine), D953G (Aspartic acid to Glycine) and L1014F (Leucine to Phenylalanine), were identified. Samples from Thailand have the three mutations, while samples from Australia and India have both M918I and L1014F mutations. Only the L1014F mutation was evident in the samples from Malaysia and Africa. The M918I and L1014F were assumed to be kdr mutations and contribute to the high pyrethroid resistance in C. hemipterus. Further studies are in process to determine the non-kdr type resistance mechanisms.